Hello @vsa18-10-90mail-ru,
Thank you very much for the login detail but when we tried to access the backend, we were unable to do as you can see in the screenshot below:
https://prnt.sc/ti7qeu
So can you please check and provide us with the correct URL so that we could log in and find the exact cause of the issue?
Also, have you added the custom tab?
Hoping to hear from you soon.
Thank you.